1. Field of the Invention
The present invention relates to a maskless lithography system for direct, nano-scale capable structuring of a substrate disposed on a movable mounting table in a vacuum chamber supplied with a high voltage, using a charged particle beam generated by a beam source, and an addressable digital pattern generating system onto which the structure pattern to be generated is transmitted as a set of pattern data generated with computer assistance using a data transmission system.
2. Brief Description of Related Art
Particle beam lithography plays a major role in the manufacture of devices in the field of microsystem-technology and monolithically integrated circuits in electronic, opto-electronic, optical and other embodiments, and their individual components, which comprise nano-sized structures measuring 100 nanometers and less. The geometrical structure to be produced on a substrate, typically a wafer, is converted into a set of pattern data with the assistance of a computer. Said set of pattern data is either used for manufacturing a mask that cannot be changed, a large area of which is being irradiated (indirect structuring technique), or said set of pattern data is continually worked off by suitably addressing the particle beam and the mounting table, on which the substrate to be structured is disposed (direct structuring technique). The indirect structuring technique is advantageous in that it enables parallel, and therefore very fast realization of the structure pattern. It has, however, also a disadvantage because of the extremely expensive manufacturing of the masks which can only be balanced by mass production of circuit layouts, because of the transfer of errors in the mask and because of the rather complex alignment when the mask is brought into position. Therefore, at present the direct structuring technique is being intensively developed further, since it offers the great advantage of flexibility with respect to the geometrical structure patterns that can be manufactured, which makes it ultimately less costly. However, this method has the disadvantage of a relatively low through-put of substrates as a result of the slow, serial structuring process employing the particle beam. Therefore, a greatest possible parallelization is also aimed at in the direct structuring method. For achieving this parallelization, different concepts are being pursued. On one hand, a plurality of parallel particle beams may be generated; on the other hand a programmable, changeable mask comprising electrically-addressed individual elements (apertures) as a pattern generating system may be irradiated with a homogeneous particle beam having a large cross section. The data rate, which needs to be processed in this preferred concept and which comprises the data for addressing the digitized structure pattern having 600,000 mask points, for instance, which are usually irradiated several times (grey scale system, comparable to the principle of the ink jet printer), and the addressing of the mounting table, is extremely high, and easily reaches several Tbit/s, such that suitable transmission of the data rate to the pattern generating system inside the vacuum chamber of the lithography system constitutes a particular problem associated with the direct structuring technique.
U.S. Pat. No. 6,379,867 B1 discloses a lithography system that is designated “maskless” since no unchangeable, rigid mask in a conventional sense is employed. Rather, the pattern generating system is configured as a pixel panel, which comprises a plurality of addressable individual elements, for instance, formed by digital mirror devices (DMD), which either transmit or block the light beam. The pattern to be generated is generated as a bitmap with the assistance of a computer, it is then stored in a storage device, and transmitted from there via a wire-bound signal connection to the pattern generating system. The data transmission system is based exclusively on a wired connection. Therefore, in order to achieve the high data transmission rate, a multitude of wire-bound data lines needs to be guided into the inside of the vacuum chamber of the lithography system, and needs to be contacted there. Thus, problems arise with the respect to their spatial arrangement and allocation, and in particular with respect to the mechanical fixation of the data lines to the carrier plate of the individual element to be addressed. Furthermore, removing the data lines for purposes of maintenance in the vacuum chamber is very complex. In addition, negative effects on the data to be transmitted may occur due to the conditions inside the vacuum chamber, in particular due to the applied high voltage.